Balanced pressure fuel valve

ABSTRACT

A hydraulic fuel valve assembly which equalizes the pressure of fluid at the hydraulic cylinder during the closed-valve condition with the pressure of fuel at the nozzle region, to thereby assure that the hydraulic cylinder is always full and to minimize variations in the force that must be applied by the hydraulic piston when fuel pressure varies. The valve assembly includes a passageway connecting the fuel supply line to the nozzle region of the valve, and a channel leading to the hydraulic cylinder to supply pressurized fuel to it. A check valve is located along the channel to prevent the flow of fluid out of the hydraulic cylinder when it is highly pressurized during valve opening. In a valve wherein a fluid other than fuel is employed in the hydraulic cylinder, a bellows or sealed piston is installed in the channel between the check valve and the fuel line to prevent mixing of the hydraulic fluid and the fuel. The valve assembly includes a valve body that forms the hydraulic cylinder, and a separate valve insert that contains a valve plunger and an insert housing that defines the valve seat and that limits plunger movement away from the seat, to thereby enable testing and adjustment prior to complete valve assembly. eBACKGROUND OF THE INVENTION 1. Field of the Invention This invention relates to valves and, more particularly, to hydraulically actuated valves. 2. Description of the prior Art One type of fuel valve employs an actuator such as a piezoelectric type whose limited motion is amplified by a hydraulic piston. The hydraulic piston has a large diameter so it can pump substantial amounts of fluid along a hydraulic cylinder. The hydraulic fluid moves a plunger of small diameter by a substantial distance to open the valve. The piezoelectric or other actuator generally must supply a pumping force sufficient to overcome a spring preload that assures that the valve will normally be closed, plus any differential pressure between the pressure of fuel at the lower end of the valve plunger and the pressure of fluid in the hydraulic cylinder prior to energization of the activator. In order to minimize the force that must be supplied by the actuator, it is desirable that the fluid pressure in the hydraulic cylinder during the valve closed condition always be approximately equal to the pressure of fuel acting on the lower end of the plunger. This balancing or equalization of pressures is particularly desirable in the case of engines which supply fuel at a widely variable pressure to permit a wide range of fuel injection rates. Such balancing is also desirable where the fuel pressure may remain stable, but where hydraulic fluid pressure may vary. For example, hydraulic pressure may fall if a temperature increase expands the hydraulic cylinder so that the hydraulic fluid cannot completely fill it, or vice versa depending upon the relative coefficients of expansion of fluid and housing. Hydraulically actuated valves are often constructed with a main housing member that forms the hydraulic cylinder in which the hydraulic piston moves, and which also forms the slider bearing hole along which the plunger slides. Additional housing members fastened to the main housing member form the valve seat and a stop that limits plunger movement during opening of the valve. This distance which the plunger moves between its open and closed states must be precisely controlled. It would be desirable to be able to test plunger operation to check for pRoper valve seating, proper opening distance and/or through flow of fuel, and smooth valve sliding, and to make appropriate adjustments, prior to assembling the complete valve.

United States Patent [191 Lilley 51 Aug. 21, 1973 123/139 AG, 123/139 AS, 123/32 AE [51] Int. Cl. F02!) 15/00 [58] Field of Search 123/32 AB, 139 R, 123/139 A, 139 B, 139 DE, 139 E, 139 AA, 139 AB, 139 AC, 139 AG, 139 AH, 139 AK, 139 AW [56] References Cited UNlTED STATES PATENTS 3,501,099 3/1970 Benson 123/32 EA Primary Examiner-Laurence M. Goodridge Attorney-Lindenberg, Freilich & Wasserman 1 ABSTRACT A hydraulic fuel valve assembly which equalizes the pressure of fluid at the hydraulic cylinder during the closed-valve condition with the pressure of fuel at the nozzle region, to thereby assure that the hydraulic cylinder is always full and to minimize variations in the force that must be applied by the hydraulic piston when fuel pressure varies. The valve assembly includes a passageway connecting the fuel supply line to the nozzle region of the valve, and a channel leading to the hydraulic cylinder to supply pressurized fuel to it. A check valve is located along the channel to prevent the flow of fluid out of the hydraulic cylinder when it is highly pressurized during valve opening. In a valve wherein a fluid other than fuel is employed in the hydraulic cylinder, a bellows or sealed piston is installed in the channel between the check valve and the fuel line to prevent mixing of the hydraulic fluid and the fuel. The valve assembly includes a valve body that forms the hydraulic cylinder, and a separate valve insert that contains a valve plunger and an insert housing that defines the valve seat and that limits plunger movement away from the seat, to thereby enable testing and adjustment prior to complete valve assembly.

14 Claims, 8 Drawing Figures Wits BALANCED PRESSURE FUEL VALVE BACKGROUND OF THE INVENTION 1. Field of the Invention This invention relates to valves and, more particularly, to hydraulically actuated valves.

2. Description of the prior Art One type of fuel valve employs an actuator such as a piezoelectric type whose limited motion is amplified by a hydraulic piston. The hydraulic piston has a large diameter so it can pump substantial amounts of fluid along a hydraulic cylinder. The hydraulic fluid moves a plunger of small diameter by a substantial distance to open the valve. The piezoelectric or other actuator generally must supply a pumping force sufficient to overcome a spring preload that assures that the valve will normally be closed, plus any differential pressure between the pressure of fuel'at the lower end of the valve plunger and the pressure of fluid in the hydraulic cylinder prior to energization of the activator. In order to minimize the force that must be supplied by the actuator, it is desirable that the fluid pressure in the hydraulic cylinder during the valve closed condition always be approximately equal to the pressure of fuel acting on the lower end of the plunger. This balancing or equalization of pressures is particularly desirable in the case of engines which supply fuel at a widely variable pressure to permit a wide range of fuel injection rates. Such balancing is also desirable where the fuel pressure may remain stable, but where hydraulic fluid pressure may vary. For example, hydraulic pressure may fall if a temperature increase expands the hydraulic cylinder so that the hydraulic fluid cannot completely fill it, or vice versa depending upon the relative coefficients of expansion of fluid and housing.

Hydraulically actuated valves are often constructed with a main housing member that forms the hydraulic cylinder in which the hydraulic piston moves, and which also forms the slider bearing hole along which the plunger slides. Additional housing members fastened to the main housing member form the valve seat and a stop that limits plunger movement during opening of the valve. This distance which the plunger moves between its open and closed states must be precisely controlled. It would be desirable to be able to test plunger operation to check for proper valve seating, proper opening distance and/or through flow of fuel, and smooth valve sliding, and to make appropriate adjustments, prior to assembling the complete valve.

OBJECTS AND SUMMARY OF THE INVENTION pressure in accordance with variations in fuel supply pressure.

Another object is to provide a hydraulic valve assembly which facilitates testing and adjustment of plunger operation prior to complete assembly.

In accordance with one embodiment of the present invention, a hydraulic valve is provided which, in the valve closed condition, assures that the pressure of fluid in the hydraulic cylinder that opens to an inner end of the plunger, equals fuel pressure applied to an outer end of the plunger that moves against the valve seat. The valve includes a passageway connecting the fuel supply line to the region where the valve seat and the outer end of the plunger are located. A channel connects the passageway to the hydraulic cylinder that opens to the inner end of the plunger. A check valve is located along the channel to prevent outflow of fuel from the hydraulic cylinder, which could occur during valve actuation. In this hydraulic valve, the fuel is utilized as the hydraulic fluid, and the channel assures that the same pressure exists at both ends of the plunger prior to energization of the hydraulic actuator, so that the actuator must supply only a minimum of force to open the valve.

In another valve constructed in accordance with the invention, a bellows is positioned along the channel between the check valve and the fuel line. The bellows permits a hydraulic fluid other than the fuel to be employed, by preventing the flow of fuel into the hydraulic cylinder. However, the bellows enables fuel pressure to be applied to the fluid in the hydraulic cylinder to equalize the pressures.

The hydraulic valve assembly is constructed in a manner that facilitates testing and adjustment of the plunger operation apart from the hydraulic cylinder portion. The assembly includes a valve body that forms the hydraulic cylinder and which holds the hydraulic piston and actuator. A separate valve insert is provided which includes an insert housing that can be received in the valve body. The insert housing forms the bearing hole along which the plunger slides, the valve seat against which the plunger closes, and a ledge that limits travel of the plunger to determine the extent to which the valve is opened. A shim is positioned between the ledge and a collar on the plunger, to facilitate precise control of the degree of valve opening. The valve insert can be fully tested for the degree of valve opening,,for proper valve seating, and for smooth valve sliding, all apart from the hydraulic cylinder, piston, and actuator apparatus.

The novel features of the invention are set forth with particularity in the appended claims. The invention will be best understood from the following description when read in conjunction with the accompanying drawrngs. I

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a sectional view of a hydraulic fuel valve assembly constructed in accordance with one embodiment of the invention;

'FIG. 2 is a view taken on the line 2-2 of FIG. 1;

FIG. 3 is a simplified view of an engine which utilizes the fuel valve assembly of FIG. 1;

FIG. 4 is a sectional side view of another valve, similar to that of FIG. 1 but with a larger valve seat and simpler valve insert;

FIG. 5 is a sectional side view of a hydraulic valve assembly constructed in accordance with still another embodiment of the invention, which employs a bellows to resist mixing of hydraulic fluid and fuel;

FIG. 6 is a view taken on the line 6-6 of FIG. 5;

FIG. 7 is a view taken on the line 7-7 of FIG. 5; and

FIG. 8 is a sectional view of a valve assembly constructed in accordance with still another embodiment of the invention, which employs a piston for transferring pressures while sealing the hydraulic fluid from mixing with the fuel.

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIGS. 1 and 2 illustrate a fuel valve assembly 10 whichcontrols the flow of fuel through a nozzle 12 into the cylinder or inlet port of an internal combustion engine. The fuel is supplied under pressure through a fuel supply line 14 to the valve assembly 10, for injection through the nozzle during a short period at every cycle of engine operation. Fuel flow through the nozzle 12 is controlled by a plunger assembly 16 that includes upper and lower plunger members 17, 19. The lower member 19 has a seating portion 18 that can move against and away from a valve seat 20. A spring 21 urges the lower plunger member in an upward direction to close the seating portion on the valve seat 20. The upper plunger member 17 is urged in an upward direction away from the lower plunger member, by a Belleville type spring washer 22. However, when an actuator 24 such as a piezoelectric or other type moves down a hydraulic piston 26 in a hydraulic cylinder 30, the piston pressurizes hydraulic fluid at the upper or inner end 28 of the plunger to force down the upper plunger member 17. The upper member 17 contacts and depresses the lower plunger member 19 to open the valve to the outflow of fuel through the nozzle 12. Thus, motion of the actuator is transmitted, with or without amplification, by the piston 26 which compresses the hydraulic fluid to move down the plunger 16.

it is desirable to maintain a pressure of fluid in the hydraulic cylinder 30, at the time when the actuator 24 is not moving and the valve is closed, which is approximately equal to the pressure of fuel in the supply line 14. One reason for this is to assure that the cylinder 30 is always filled with fluid. Another reason is to assure that the upward forcesapplied by fuel to the lower region of the plunger 16, particularly at the regions 31 thereof that are exposed to fuel pressure, are approximately counterbalanced by the pressure of fluid in the cylinder 30. This balancing of pressures assures that the force which the actuator 24 must supply does not greatly increase if fuel pressure greatly increases. In this embodiment of the invention, fuel is used as the hydraulic fluid, and a small amount of fluid can leak past the upper member of the plunger 16 into the hydraulic cylinder 30. However, the leakage may be very small so that it requires a long time to equalize the pressures. If the pressure of fuel in the supply line 14 should suddenly increase, as can happen particularly in an engine system wherein fuel supply pressure is varied over a wide range, then the much higher fuel pressure applied to the lower or outer portion (regions 31) of the plunger 16 may create such a high preload that the actuator 24 cannot supply enough force to open the valve.

in accordance with the present invention, the fuel valve is constructed to permit the rapid flow of fuel into the hydraulic cylinder 30. This influx of fuel can increase the pressure in the hydraulic cylinder if the fuel supply pressure should increase. The valve is constructed with a passageway 32 connected to the fuel supply line 14, which leads to the region of the valve seat 20. A channel 36 leads from the passageway 32 to the hydraulic cylinder 30. Fuel can flowthrough the channel 36 to rapidly supply fuel to completely fill the hydraulic cylinder and to transfer any increase in fuel supply pressure to it. A check valve 38 is located along the channel 36 to prevent the outflow of fuel from the hydraulic cylinder during the period in each cycle when the actuator 24 is activated to pressurize the hydraulic fluid so as to open the valve.

The check valve 38 prevents the outflow of fuel from the hydraulic cylinder, so that any outflow must pass along the upper member 17 of the plunger 16. The clearance along the upper plunger member 17 is small so that only a small outflow can occur. Thus, if the pressure in the supply line 14 is suddenly reduced, the pressure in the hydraulic cylinder 30 cannot decrease very rapidly and the plunger 16 may open slightly sooner and close slightly later than would be desired. However, the Belleville washer 22 supplies a sufficiently high spring force to prevent a constant valve opening in this situation and the pressure will soon equalize. It may be noted that the Belleville washer 22 has a substantial preload to assure rapid plunger movement under normal conditions, and this preload is sufficient to prevent a valve open condition when the fuel supply pressure suddenly drops.

In the construction of the fuel valve, close tolerances must be maintained to assure proper seating of the valve closing portion 18 on the valve seat 20, and to closely control the amount by which the closing portion 18 moves away from the seat during the valve open condition. It would be desirable to enable testing and adjustment of the plunger portion of the valve for proper seating and magnitude of opening under operating condition, prior to assembly in the complete valve apparatus that includes the actuator and hydraulic pumping apparatus. To enable this, the valve assembly 10 is constructed with a main valve body 40 that holds the actuator 24 and a cap 42 thereon, the valve body also forming the hydraulic cylinder 30, the passageway 32 that is connected to the fuel line 14 and the channel 36 that carries the check valve 38. A separate valve insert 44 is provided which includes a valve insert housing 46 that can be received in a receiving portion 48 of the main valve body 40. The upper plunger member 17 has a central portion 50 that can slide along a bearing hole 52 formed in the valve insert housing 46. A valve seat 54 is held at one end of the insert housing'by a cap 56. As fuel-receiving groove 51 is formed in the insert housing, and an aperture 53 carries fuel from the groove 51 for passage to the valve seat. A pair of seal grooves 55 hold O-rings to prevent the escape of fuel.

The upper or inner portion 28 of the plunger carries a collar 58 held thereon by a snap ring retainer 60. The collar 58 bears against the Belleville washer 22, and the washer bears against a shim 62 that lies against a ledge 64 formed on the insert housing 46.

In order to precisely control the distance which the plunger 16 moves to the valve open condition, it ordinarily would be necessary to locate the collar 58 at a closely controlled distance from the valve closing portion 18 of the plunger (when the upper and lower plunger members 17, 19 are in contact), and also to precisely control the distance between the ledge 64 and the valve seat 20. Since these distances are long while the distance of plunger movement to the valve open condition is short, it is very difficult to closely control the amount of valve opening. Close tolerances can be maintained by the use of the shim 62. A shim 62 of appropriate thickness is employed to provide the required space between the bottom surface 66 of the collar and the upper surface of the shim, to provide the proper distance of valve opening. The assembled valve insert 44 can be tested under operating conditions on a test set up to check for proper operation, and the shim 62 can be replaced by other shims of slightly different size to achieve proper operation. The valve insert 44 can then be inserted into the main valve body 40 to complete the hydraulic fuel valve assembly. Normally, the clearance between the plunger portion 50 and the bearing hole 52 in which it slides, the seating of the valve closing portion 18 on the seat 20, and the distance of plunger travel to the valve open condition will not be affected by the rest of the valve apparatus.

FIG. 3 illustrates, in highly simplified form, an engine which utilizes the hydraulic fuel valve assembly to supply fuel to flow with air through another valve 63 into a combustion cylinder or chamber 61, where the fuel and air are burned to drive a piston 65 that delivers engine output power. Fuel from a fuel tank 67 is pressurized by a pump 68 that delivers the fuel to the fuel valve assembly 10. A control 70 varies the pressure supplied by the fuel pump 68. The pump 68 may supply fuel over a wide range such as 50 to 500 psi to enable close control of the amount of injected fuel at both very low and very high engine loads. The construction of the fuel valve to balance the pressure in the hydraulic cylinder with the fuel pressure enables the actuator to open the valve even during a rapid increase in pressure, as well as assuring that the hydraulic cylinder is always filled. It should be noted that the valve assembly can be employed in a variety of engine configurations, including those with direct injection where the fuel is injected through a nozzle directly into the cylinder, those where the fuel is injected through the same port as that through which air enters the cylinder, those where fuel is injected into the intake air stream,as well as other types.

FIG. 4 illustrates a valve constructed in accordance with another embodiment of the invention, which is similar to the valve of FIG. 1 except that the valve seat 20A is formed on the valve insert housing 46A and is of larger size. The valve closing portion 18A is correspondingly larger. This enables the plunger 16A to be installed through the bearing hole 52A in the valve insert without the need for an additional valve seat member or cap to hold it in place.

F lGS. 5 through 7 illustrate a valve assembly 80 constructed in accordance with still another embodiment of the invention, wherein the hydraulic fluid which is pumped to move the valve plunger, is a fluid other than the fuel which is injected through the valve. The valve includes a main housing 82 which has a passageway 84 connecting the fuel line 12 to the valve seat for injection of the fuel into the cylinder or air intake port of the engine. A channel 88 connects the passageway to a hydraulic cylinder 90. The channel 88 has an enlarged region 92 with a bellows 94 therein. The inside of the bellows contains fuel while the outside of the bellows is in contact with hydraulic fluid 96. The channel 88 includes a portion 98 that leads from the enlarged region 92 through a check valve 101 to the hydraulic chamber. The bellows 94 can expand and contract to equalize the fluid pressure on either side thereof, so as to equalize the pressure of fuel in the channel portion leading to the bellows with the pressure of hydraulic fluid 96 located outside of the bellows and in the hydraulic cylinder. The enlarged region 92 of the channel serves as a reservoir for supplying any hydraulic fluid that is required to completely fill the hydraulic cylinder, if the volume of the cylinder should increase more than the volume of fluid therein during heating or cooling of the valve assembly. The reservoir provided by the enlarged region 92 also can supply any hydraulic fluid that might leak out of the hydraulic cylinder. However, the plunger assembly is constructed to minimize such leakage.

As best shown in FIG. 6, the plunger assembly 100 has a narrow region 102 that is sealed by an O-ring 104 to the walls of the slider bearing hole 106 along which the plunger slides, to largely eliminate loss of hydraulic fluid. A small flow of hydraulic fluid can occur past an upper plunger portion 107 to a conduit 89 that leads to a portion of the channel 88 between the check valve and the bellows. A flange 106 on the plunger can abut a ledge 108 on a housing member 110 to limit the plunger travel during a valve open condition, and thereby control the degree of valve opening. A pair of springs 112, 114 urge the valve towards the closed condition. A valve closing member 116 can move against a valve seat 118 on a seat member 120 that is held in place by a cap 122.

FIG. 8 illustrates a fuel valve similar to the valve of FIGS. 5-7, except that a piston is employed that slides along an enlarged region 92 of the second passageway portion 88, instead of a bellows. The piston 130 is freely slideable so that it moves in response to any substantial pressure differential between the fuel supply pressure and the pressure of hydraulic fluid in the hydraulic cylinder during the valve closed condition. The piston 130 has O-ring seals 132 that resist leakage of fluid across the piston.

Thus, the invention provides a hydraulic fuel valve assembly that maintains a pressure of hydraulic fluid in the hydraulic cylinder that depends upon the pressure of fuel supplied to the valve for controlled flow therethrough. The valve serves to keep the hydraulic cylinder completely filled during the valve closed condition. The valve also serves to vary the pressure of hydraulic fluid in accordance with variations in pressure of the fuel supplied to the valve for injection, thereby minimizing the force which must be supplied by the actuator to open the valve.

Variation of hydraulic chamber pressure at the initial or valve closed condition in accordance with variations in fuel pressure is especially important in the case of engines wherein the fuel supply pressure may vary within wide limits. The valve achieves these functions by coupling the fuel supply line to the hydraulic cylinder or chamber, to transmit fuel pressure variations to the hydraulic chamber. In those valves where the fuel serves as a hydraulic fluid, the coupling can allow fuel to move into and out of the hydraulic chamber. Where a hydraulic fluid other than fuel is employed, means such as a bellows or sealed but moveable piston is employed to transmit fluid pressure while sealing against the passage of fluid therethrough.

Although particular embodiments of the invention have been described and illustrated herein, it is recognized that modifications and variations may readily occur to those skilled in the art and, consequently, it is intended that the claims be interpreted to cover such modifications and equivalents.

What is claimed is:

1. An engine comprising:

a fuel tank;

means defining a combustion chamber;

valve housing means including a hydraulic cylinder for holding fluid, a slide beefing hole and a valve seat;

means for carrying fuel passing out from said valve seat to said combustion chamber;

piston means positioned at said hydraulic cylinder;

means for controllably moving said piston means to pressurize fluid in said hydraulic cylinder;

plunger means slideably mounted in said bearing hole and having an inner end portion exposed to fluid in said hydraulic cylinder and an outer end movable against and away from said valve seat;

' a fuel supply line coupling said fuel tank to said valve housing means;

said housing means including a passageway coupling said fuel supply line to said valve seat;

means defining a channel coupling said fuel supply line to said hydraulic cylinder; and

means disposed along said channel for blocking the flow of fluid in a direction away from said hydraulic cylinder.

2. An engine comprising:

fuel tank means for holding fuel;

a fuel supply line coupled to said fuel tank means;

means defining a combustion chamber;

hydraulic cylinder means for holding a fluid;

piston means controllably movable against fluid in said cylinder means to pressurize it;

means defining a valve seat;

means for coupling said valve seat to said combustion chamber;

slideably mounted plunger means having a first portion coupled to fluid in said hydraulic cylinder means for movement by the pressure of said fluid, and having a second portion with closing means for alternately seating upon and moving away from said valve seat;

means defining a passageway for coupling said fuel supply line to said valve seat to allow fuel to pass out across said valve seat when said closing means is away from said valve seat; and

means coupling said supply line to said hydraulic cylinder means for varying the pressure in said hydraulic cylinder means in accordance with the pressure of fuel in said supply line, at least at times when said piston means is not moving to pressurize fluid in said hydraulic cylinder means.

3. The engine described in claim 2 wherein:

said means coupling said supply line to said hydraulic cylinder means includes a channel for carrying fuel from said supply line into said hydraulic cylinder, and a check valve disposed along said channel for allowing fuel flow therethrough only in a direction towards said hydraulic cylinder means.

4. The engine described in claim 2 wherein:

said means coupling said supply line to said hydraulic cylinder means includes a movable member having opposite sides respectively coupled to said hydraulic cylinder means and to said supply line to move in response to the pressure differential thereacross, said movable member sealed against the flow of fluid from one side thereof to the other, whereby to enable an equalization of pressure while maintaining a fluid other than said fuel in said hydraulic cylinder means.

5. An engine comprising:

a fuel tank;

a fuel supply line coupled to said fuel tank;

a combustion chamber;

valve housing means including a hydraulic cylinder for holding fuel, a valve seat coupled to said combustion chamber, and a slider bearing hole between said cylinder and seat;

plunger means slideably mounted in said slider hearing hole, said plunger means having an inner end for receiving the pressure of fluid in said hydraulic cylinder and an outer end, and having valve closing means at said outer end for moving against and away from said valve seat;

said valve housing means defining a passageway coupling said fuel supply line to said valve seat to flow fuel across it when said valve closing means is away from said seat, and a channel leading to said hydraulic cylinder; and

check valve means disposed along said channel, for

substantially preventing the flow of fuel therethrough in a direction away from said hydraulic cylinder.

6. The engine described in claim 5 including:

sealed pressure transfer means disposed along said channel on aside ofxsaid check valve means furthest from said hydraulic cylinder, for preventing the transfer of fluid between said fuel supply line and said hydraulic cylinder while raising the pressure of fluid in said hydraulic cylinder in response to increases in the pressure of fuel in said fuel supply line.

7. The hydraulic fuel valve assembly described in claim 6 including:

a fluid conduit coupling said bearing hole to a region of said channel between said check valve means and said sealed pressure transfer means.

8. The engine described in claim 5 including:

a bellows disposed along said channel on a side of said check valve means furthest from said hydraulic cylinder.

9. The hydraulic fuel valve assembly described in claim 5 including:

a freely movable piston slideably mounted along a region of said channel which is on a side of said check valve means furthest from said hydraulic cylinder.

10. The hydraulic fuel valve assembly described in claim 5 wherein:

said valve housing means includes a valve body forming said hydraulic cylinder and forming an insertreceiving portion, and an insert housing received in said receiving portion of said valve body and forming said slider bearing hole and said valve seat, said insert housing also forming a ledge at an end of said bearing hole nearest said pump chamber;

said plunger means has a collar at said inner end for moving towards and away from said ledge; and including a spring washer disposed against said collar on said plunger means; and

a shim disposed between said ledge and spring washer.

11. An engine comprising:

means for holding fuel including a fuel supply line;

a combustion chamber;

a valve body having a hydraulic cylinder portion, a

receiving portion in communication with said cylinder portion, and a fuel passage connected to said fuel supply line and leading to said receiving portion;

a piston disposed in said hydraulic cylinder portion for pumping fluid out of said cylinder portion towards said receiving portion; and

a valve insert assembly including a housing at least partially received in said receiving portion of said valve body, said housing having walls defining an elongated slider bearing hole with inner and outer end portions respectively nearest and furthest from said piston, said ledge adjacent to said inner portion of said slider bearing hole, and a valve seat adjacent to said outer portion of said slider bearing hole, said valve seat having a first side coupled to said fuel passage and a second side coupled to said combustion chamber; and

valve plunger means slideably mounted in said bearing hole and having inner and outer portions, said plunger means including a valve seating portion for seating upon and unseating from said valve seat as said valve plunger means moves towards and away from said inner portion of said bearing hole, respectively, and also including a collar at said inner portion of said plunger for moving towards and away from said ledge, so that the maximum valve opening as defined by the maximum distance of said valve seating portion from said valve seat is determined, at least in part, by the length of said housing between said ledge and valve seat in relation to the length of said plunger means between said collar and seating portion, whereby the valve insert can be tested and precisely adjusted for a de' sired maximum valve opening prior to installation in the valve body.

12. The engine described in claim 11 including:

a shim disposed between said ledge and flange, whereby to facilitate precise adjustment of the maximum valve opening.

13. The engine described in claim 11 wherein:

said housing of said insert has a fuel-receiving groove on its outside for holding fuel between the housing and said valve body, a pair of seal-receiving grooves on its outside at either end of said fluidreceiving grooves, and an aperture leading from said fluid-receiving groove to said bearing hole to carry fuel for flowing to said valve seat, and said insert includes a pair of elastomeric seal rings disposed in said seal-receiving grooves; and

said fuel passage is coupled to said fuel receiving groove for carrying fuel thereto.

14. The valve assembly described in claim 13 including:

walls defining a channel in said valve body, which connects said passageway to said hydraulic cylinder portion; and

check valve means disposed along said channel for allowing fuel flow only toward said hydraulic cylinder portion, whereby to vary the initial force tending to open said valve in accordance with fuel supply pressure. 

1. An engine comprising: a fuel tank; means defining a combustion chamber; valve housing means including a hydraulic cylinder for holding fluid, a slide bearing hole and a valve seat; means for carrying fuel passing out from said valve seat to said combustion chamber; piston means positioned at said hydraulic cylinder; means for controllably moving said piston means to pressurize fluid in said hydraulic cylinder; plunger means slideably mounted in said bearing hole and having an inner end portion exposed to fluid in said hydraulic cylinder and an outer end movable against and away from said valve seat; a fuel supply line coupling said fuel tank to said valve housing means; said housing means including a passageway coupling said fuel supply line to said valve seat; means defining a channel coupling said fuel supply line to said hydraulic cylinder; and means disposed along said channel for blocking the flow of fluid in a direction away from said hydraulic cylinder.
 2. An engine comprising: fuel tank means for holding fuel; a fuel supply line coupled to said fuel tank means; means defining a combustion chamber; hydraulic cylinder means for holding a fluid; piston means controllably movable against fluid in said cylinder means to pressurize it; means defining a valve seat; means for coupling said valve seat to said combustion chamber; slideably mounted plunger means having a first portion coupled to fluid in said hydraulic cylinder means for movement by the pressure of said fluid, and having a second portion with closing means for alternately seating upon and moving away from said valve seat; means defining a passageway for coupling said fuel supply line to said valve seat to allow fuel to pass out across said valve seat when said closing means is away from said valve seat; and means coupling said supply line to said hydraulic cylinder means for varying the pressure in said hydraulic cylinder means in accordance with the pressure of fuel in said supply line, at least at times when said piston means is not moving to pressurize fluid in said hydraulic cylinder means.
 3. The engine described in claim 2 wherein: said means coupling said supply line to said hydraulic cylinder means includes a channel for carrying fuel from said supply line into said hydraulic cylinder, and a check valve disposed along said channel for allowing fuel flow therethrough only in a direction towards said hydraulic cylinder means.
 4. The engine described in claim 2 wherein: said means coupling said supply line to said hydraulic cylinder means includes a movable member having opposite sides respectively coupled to said hydraulic cylinder means and to said supply line to move in response to the pressure differential thereacross, said movable member sealed against the flow of fluid from one side thereof to the other, whereby to enable an equalization of pressure while maintaining a fluid other than said fuel in said hydraulic cylinder means.
 5. An engine comprising: a fuel tank; a fuel supply line coupled to said fuel tank; a combustion chamber; valve housing means including a hydraulic cylinder for holding fuel, a valve seat coupled to said combustion chamber, and a slider bearing hole between said cylinder and seat; plunger means slideably mounted in said slider bearing hole, said plunger means having an inner end for receiving the pressure of fluid in said hydraulic cylinder and an outer end, and having valve closing means at said outer end for moving against and away from said valve seat; said valve housing means defining a passageway coupling said fuel supply line to said valve seat to flow fuel across it when said valve closing means is away from said seat, and a channel leading to said hydraulic cylinder; and check valve means disposed along said channel, for substantially preventing the flow of fuel therethrough in a direction away from said hydraulic cylinder.
 6. The engine described in claim 5 including: sealed pressure transfer means disposed along said channel on a side of said check valve means furthest from said hydraulic cylinder, for preventing the transfer of fluid between said fuel supply line and said hydraulic cylinder while raising the pressure of fluid in said hydraulic cylinder in response to increases in the pressure of fuel in said fuel supply line.
 7. The hydraulic fuel valve assembly described in claim 6 including: a fluid conduit coupling said bearing hole to a region of said channel between said check valve means and said sealed pressure transfer means.
 8. The engine described in claim 5 including: a bellows disposed along said channel on a side of said check valve means furthest from said hydraulic cylinder.
 9. The hydraulic fuel valve assembly described in claim 5 including: a freely movable piston slideably mounted along a region of said channel which is on a side of said check valve means furthest from said hydraulic cylinder.
 10. The hydraulic fuel valve assembly described in claim 5 wherein: said valve housing means includes a valve body forming said hydraulic cylinder and forming an insert-receiving portion, and an insert housing received in said receiving portion of said valve body and forming said slider bearing hole and said valve seat, said insert housing also forming a ledge at an end of said bearing hole nearest said pump chamber; said plunger means has a collar at said inner end for moving towards and away from said ledge; and including a spring washer disposed against said collar on said plunger means; and a shim disposed between said ledge and spring washer.
 11. An engine comprising: means for holding fuel incLuding a fuel supply line; a combustion chamber; a valve body having a hydraulic cylinder portion, a receiving portion in communication with said cylinder portion, and a fuel passage connected to said fuel supply line and leading to said receiving portion; a piston disposed in said hydraulic cylinder portion for pumping fluid out of said cylinder portion towards said receiving portion; and a valve insert assembly including a housing at least partially received in said receiving portion of said valve body, said housing having walls defining an elongated slider bearing hole with inner and outer end portions respectively nearest and furthest from said piston, said ledge adjacent to said inner portion of said slider bearing hole, and a valve seat adjacent to said outer portion of said slider bearing hole, said valve seat having a first side coupled to said fuel passage and a second side coupled to said combustion chamber; and valve plunger means slideably mounted in said bearing hole and having inner and outer portions, said plunger means including a valve seating portion for seating upon and unseating from said valve seat as said valve plunger means moves towards and away from said inner portion of said bearing hole, respectively, and also including a collar at said inner portion of said plunger for moving towards and away from said ledge, so that the maximum valve opening as defined by the maximum distance of said valve seating portion from said valve seat is determined, at least in part, by the length of said housing between said ledge and valve seat in relation to the length of said plunger means between said collar and seating portion, whereby the valve insert can be tested and precisely adjusted for a desired maximum valve opening prior to installation in the valve body.
 12. The engine described in claim 11 including: a shim disposed between said ledge and flange, whereby to facilitate precise adjustment of the maximum valve opening.
 13. The engine described in claim 11 wherein: said housing of said insert has a fuel-receiving groove on its outside for holding fuel between the housing and said valve body, a pair of seal-receiving grooves on its outside at either end of said fluid-receiving grooves, and an aperture leading from said fluid-receiving groove to said bearing hole to carry fuel for flowing to said valve seat, and said insert includes a pair of elastomeric seal rings disposed in said seal-receiving grooves; and said fuel passage is coupled to said fuel receiving groove for carrying fuel thereto.
 14. The valve assembly described in claim 13 including: walls defining a channel in said valve body, which connects said passageway to said hydraulic cylinder portion; and check valve means disposed along said channel for allowing fuel flow only toward said hydraulic cylinder portion, whereby to vary the initial force tending to open said valve in accordance with fuel supply pressure. 